This invention is related to sewage treatment, and more specifically, to a method of and an apparatus for treating and disposing of sewage in cold regions.
Historically, sewage treatment in cold regions has been plagued by problems. Cold regions include Arctic, subArctic, and Antarctic regions. One problem common in many cold regions is permanently frozen soil, or permafrost. The placement of foreign objects on top of or within permafrost may, over time, cause melting of the permafrost, which in turn can cause sinking, settling or collapse of the soil.
In more temperate regions, underground treatment systems such as septic tanks with soil absorption systems have been used. However, in cold regions such underground systems are not feasible for several reasons. Permafrost may preclude the use of underground systems as it may prevent digging, or the placement of an underground system may thaw the permafrost. Placing the systems above ground would generally provide too cold of an environment for proper sewage treatment, and might still melt the permafrost below. Even the addition of external heat sources to such systems is generally not feasible, as such heat sources would have a greater thawing effect on the permafrost.
Permafrost, and the accompanying frigid conditions above ground that are typical in cold regions, have greatly reduced the viability of traditional sewage systems. One common solution in remote areas has been the xe2x80x9choney bucketxe2x80x9d system, where sewage is stored in a tank or other receptacle, and periodically collected from the individual tanks and taken to a centralized sewage treatment facility. This necessitates a vehicle and personnel to collect and haul the sewage, and an enclosed sewage treatment facility, all of which are typically quite expensive. In addition, the individual tanks or receptacles face the possibility of freezing, overflow, or other failure, and thereby pose a health risk to not only the individual user but also the surrounding community.
Another approach has been to use a traditional septic tank, but with an above ground leach field, called a soil absorption mound. However, the heat from the septic tank, or the pipes, or even the absorption mound, may cause melting of the permafrost, and differential movement of the components, such that pipes may become dislodged or break away from the tank or the mound, causing spillage and failure of the system. In addition, where the ground is frozen, the effluent may not flow down into the ground, but instead flow horizontally outside of the mound, with the anaerobically treated effluent giving off a strong odor.
A more advanced approach has been to build more traditional sewage collection systems, which route the sewage to a centralized sewage treatment facility. However, the components of such a system are still subject to the dangers of permafrost. Permafrost may hamper the ability to dig and bury such collection systems, and if such systems are placed above ground, the heat generated may still cause melting of the permafrost, and the accompany differential movement of the collection system may cause leakage and/or failure. In addition, a centralized sewage treatment center must be constructed and operated, generally at great expense, as it must typically be enclosed in a heated building.
Thus there exists the need for a sewage treatment system, and a method for treating sewage, usable in cold regions and/or above or within permanently frozen ground, which will operate efficiently, in a safe and sanitary way, to treat the sewage in a cost-effective manner. cl SUMMARY OF THE INVENTION
The present invention is embodied in a method and apparatus for treating sewage utilizing a multi-compartment sewage treatment system which operates in cold regions, above and/or within frozen ground, using a combination of fresh and recirculated air to aerobically treat the sewage to the extent that the effluent may be discharged directly to the environment, all while avoiding cold-related failure, and without the need for an external heat source.
The sewage treatment system provides a pretreatment compartment, having an inlet and an outlet, an aerobic treatment compartment, containing an aerobic sewage treatment unit, and also having an inlet and outlet, such that the inlet of the aerobic treatment compartment is coupled to the outlet of the pretreatment compartment to permit flow of sewage between the two.
An important feature of this invention is that the compartments of the system can be enclosed in a single insulated tank, and thus can be used above permafrost without thawing the frozen soil.
Another feature of the present invention is that the system may include a blower, having a first air inlet and a second air inlet, both coupled to an air outlet, such that the first air inlet draws in air from outside the sewage treatment system, and the second air inlet draws in and recirculates air from inside the sewage treatment system. The air outlet is coupled to the aerobic sewage treatment unit to permit air flow through the aerobic sewage treatment unit.
An advantage of this feature is that the combination of the coupled compartments and the blower act to contain the heat from both the sewage itself and the blower, to heat the entire system, prevent freezing, and provide air to the aerobic treatment unit at the proper temperature.
Another advantage of the system is that it is energy efficient, as powering the blower uses approximately the same amount of energy as powering a large lightbulb, with a very small energy requirement to treat the sewage and keep it thawed.
Another feature of the present invention is that the system may include a discharge compartment, which holds the treated sewage until it is discharged.
Another feature of the present invention is that the system may include a dosing siphon within the discharge compartment to discharge the treated sewage. An advantage including a dosing siphon is that the effluent is released in xe2x80x9cslugsxe2x80x9d or xe2x80x9cbatchesxe2x80x9d and thus does not freeze up or xe2x80x9cglacierxe2x80x9d within the discharge line or at the point of discharge, but instead flows out through the discharge line in intermittent, high volume, high flow rate discharges.
Another advantage of the discharge compartment is that it may also contain disinfecting equipment, so that the treated sewage may be disinfected before it is discharged.
Another advantage of the present invention is that it is much more environmentally sensitive than typical septic tanks, with the effluent having significantly lower BOD5, (5 day Biochemical Oxygen Demand) and total suspended solids concentrations than the effluent of a typical septic system. In addition, because the sewage has been aerobically treated, the effluent does not have the odor common to the anaerobically treated effluent of a septic system.
Another advantage of this present invention is that although it was originally designed for use above permafrost, it can also be used advantageously in areas of shallow bedrock, layers of clay, or in other situations where subsurface discharge of treated sewage is ineffective, impossible or prohibitively costly.
Another advantage of the present invention is that it is relatively inexpensive, does not require specialized indoor plumbing configurations or fixtures, and is simple and requires little maintenance.
Another advantage of the present invention is that it is adaptable to a variety of temperature conditions, does not need to be enclosed in a building, and is scalable depending on the design sewage load.
Another advantage of the present invention is that it can be used as a temporary, above-ground sewage treatment system to replace failed septic systems, especially in cold regions where the frozen ground may make it virtually impossible to dig out and replace a failed septic system.
Another advantage of the present invention is that by utilizing surface discharge, and by recovering a portion of the latent heat from the sewage, less heat is input back into the environment, thereby further reducing the risk of thawing the permafrost.
Another advantage of the present invention is the above-ground configuration provides accessability, and in the event of a malfunction, the surface discharge provides an instantaneous, malodorous notification.
Another feature of this invention is that by incorporating the entire system, including the pretreatment compartment, the aerobic treatment compartment and the discharge compartment into a single tank, in the event of ground movement due to thawing of permafrost, or even earthquake, differential movement of the system components is prevented.
Other features and advantages of the present invention will become apparent from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention.